Generally, when a driver drives a vehicle in defile, the driver can use a side mirror of the vehicle or a room mirror mounted in the inside of the vehicle, or can directly use the naked eye to recognize a surrounding situation.
However, if the vehicle moves forward or backward in the defile, there exists a blind spot, in which the driver cannot see the entire surrounding area, in the front or rear sides of the vehicle even while using the side mirror or the rearview mirror or the naked eye. Therefore, a fender bender or damage of the vehicle can occur.
In addition, since many vehicles are parked or stopped in a narrow parking area, such as alleys in residential district, an unexpected defile often exits. Thus, it is difficult to drive vehicles on narrow streets and alleys due to the unexpected defile.